CTP screen printing has the following features: (1) Reduce the plate making process and achieve the goal of rapid plate making. (2) Save film, because no film is needed, so as to prevent the quality problems caused by film wear and network level loss. (3) Screen positioning can be performed automatically for multicolor screen printing. (4) The inkjet coating does not require a special photosensitive adhesive, and the commonly used photosensitive adhesive is suitable. (5) The screen version of various meshes can be done. (6) All kinds of frame, aluminum alloy frame and wooden frame can be used. (7) Plate making up to 66x96.5 cm. Screen printing CTP direct plate making principle is the use of computer digital processing technology to design the required screen printing image, after modification, finalized and stored in the computer. At the time of plate making, a laser ink jet printer was used to print the image on a screen previously coated with a photosensitive resin. This screen is called a pre-printed version (screen printing PS version). The ink-receiving image on the screen acts as a film or a cover film, and then the entire screen is exposed with ultraviolet light (stencil printing). The ink is partially exposed to ultraviolet light, and no chemical reaction occurs, resulting in a difference in solubility. After the same as the traditional photoengraving principle, exposure, development and imaging imaging plate. Please refer to screen printing CTP plate making process diagram. Screen printing CTP plate, screen printing presensitized photosensitive emulsion used in the photosensitive layer, the general traditional all kinds of screen printing with photosensitive adhesive can be used. The requirements for laser ink jet ink are many, but the main two points are: (1) The ink density and ink ejection amount are based on the final image optical density of 3.0 or more. (2) The connecting resin for ink is preferably water-soluble so that water can be removed during development. However, if the photoresist is positive, the ink-based resin should be oil-soluble. Now Polaroid and Gerber Technologies of the United States have all developed such CTP platesetters. The United States Gerber technology company developed the computer digital without film CTP platemaking machine. The plate-making machine can be connected with a personal computer. The necessary plate-making graphics and characters are input to the disk, and the disk is placed on the plate-making machine. After the plate-making machine is started, the computer-controlled ink-jet device mounted on the machine will follow the input. The image text is automatically sprayed on the screen that has been coated with photoresist. Injected by the ink jet device, of course, is not ink, but a special coating material, which can play exactly the same role as the traditional film printing. In addition to the Gerber company in the United States, Denmark has also successfully developed a digital computer-less film CTP platemaking machine, the development of the machine is the Danish Mografa (MOGRAFA) company. It differs from the United States Gerber plate making machine in that the output graphic uses a laser-generated point-like exposure method, and the computer-generated graphic message is directly hit on a screen plate that has been coated with a good photoresist for exposure printing. Rinse and develop the screen plate. This kind of direct plate making method can also save the costs of film, medicine, and amplification, and avoid the undesirable phenomena such as dust pollution and blowholes generated in the conventional plate making process. A blackboard (also known as a Chalkboard) is a reusable writing surface on which text or drawings are made with sticks of calcium sulphate or calcium carbonate, known, when used for this purpose, as chalk. Blackboards were originally made of smooth, thin sheets of black or dark grey slate stone. Wooden Chalkboard,Wooden Blackboard,Wooden Sandwich Board,Chalkboard Sign Jinan Tri-Tiger Technology Development Co., Ltd , https://www.tritigerwooden.com
A blackboard can simply be a board painted with a dark matte paint (usually black, occasionally dark green).Matte black plastic sign material (known as closed-cell PVC foamboard) is also used to create custom chalkboard art.Blackboards on an A-frame are used by restaurants and bars to advertise daily specials.
A more modern variation consists of a coiled sheet of plastic drawn across two parallel rollers, which can be scrolled to create additional writing space while saving what has been written. The highest grade blackboards are made of a rougher version porcelain enamelled steel (black, green, blue or sometimes other colours). Porcelain is very hard wearing, and blackboards made of porcelain usually last 10–20 years in intensive use.
Lecture theatres may contain a number of blackboards in a grid arrangement.The lecturer then moves boards into reach for writing and then moves them out of reach, allowing a large amount of material to be shown simultaneously.
The chalk marks can be easily wiped off with a damp cloth, a sponge or a special blackboard eraser usually consisting of a block of wood covered by a felt pad. However, chalk marks made on some types of wet blackboard can be difficult to remove. Blackboard manufacturers often advise that a new or newly resurfaced blackboard be completely covered using the side of a stick of chalk and then that chalk brushed off as normal to prepare it for use.